Saturday, April 20, 2013

Vultures- a wake and a venue

Last week, there was a wake (what a group of vultures on the ground are called) of mostly Black Vultures (Coragyps atratus) in my neighbor's yard. There was only one Turkey Vulture (Cathartes aura), poor guy. Turkey Vultures have a better sense of smell than Black Vultures- and the Black Vultures often follow them to a carcass and are quite successful at crowding out the lone Turkey Vulture. In this case, a well-rotted Possum body was the center of contention.
Both roost in large groups, and I have in the past dissuaded them from roosting in our trees in the pocket swamp because of their copious and very stinky poops- apparently, their feces can hurt or even kill trees. I would go out at twilight, and bang a wooden spoon on a cast iron skillet, it's so loud, I had to wear earplugs. They didn't like it one bit.
A venue of vultures roosting in trees is very quiet, they only rarely hiss or make a low grunt sound.The tip off that there are vultures overhead is when they get nervous, they rustle their wings, which creates a sound much like the biggest taffeta skirt in the world. Very creepy. Glad I never traumatized them too much, if they really get upset- they puke up all the rotten meat that they have just consumed.
A group of vultures is called a wake, committee, venue, kettle, or volt. The term kettle refers to vultures in flight, while committee, volt, and venue refer to vultures resting in trees. Wake is reserved for a group of vultures that are feeding,-quite apropos.
Both populations live in the Tampa area year round. At different times of the year- usually spring- they are more obvious. It has been a point of much discussion (and mirth) that our resident vultures like to roost during the day on the top of the county courthouse.
New World Vultures are genetically different from Old World Vultures, but very similar in appearance and structure because of convergent evolution. The mostly naked head and neck are convenient when digging into stinky carrion, a typical Old and New World Vulture feast; this is an example of analogous structure (i.e., when the same traits evolve independently in unrelated groups). The bald heads are an important part of hygiene for vultures.
Although both roost in large groups, the Turkey Vulture tends to strike out alone when searching for the next rotting carcass, Black Vultures tend to go out in groups- thus disadvantaging the Turkey Vulture you see in the photos, up in a tree watching the black headed bullies finish off his find.
Vultures are very elegant when flying, soaring on updrafts like elegant black parentheses against the blue sky, seemingly for hours at a time. On the ground, they are quite ungainly- the Turkey Vulture more so- they half lope and hop. The Black Vultures can stride along pretty well, but even they tend to flap a lot and almost crash when attempting to land.
For some odd reason, people in the south refer to Turkey Vultures as Buzzards, This may be because the original English colonists were familiar with Buzzards (what they called any large, soaring bird of prey), an interesting linguistic holdover.
Vultures are an essential part of the ecosystem, they help clean up dead animals that could contaminate water and poison other animals. These birds are of great value as scavengers, especially in hot regions. Vulture stomach acid is exceptionally corrosive, this allows them to safely digest putrid carcasses infected with bacteria that would be lethal to other scavengers.

Turkey Vulture up in a tree, watching while the marauding Black Vultures devour his prize. Turkey Vultures are various shades of brown and have a bright red head and neck, devoid of all feathers. Their legs are white because they pee on their legs in the summer to cool off- this also helps to to kill any bacteria left over from wading into decaying tissues while feeding.

Black Vultures strutting around the corpse. They are solid black except for a lighter feathers at the wing tip (most obvious when flying). Their heads are a dark charcoal gray, with no feathers.The last photograph shows their strutting style.

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All photographs courtesy of Catherine L. Thompson unless otherwise noted and acknowledged and are protected by copyright. Please do not use, copy or reproduce any of my images without my explicit permission.